Wed·Sep 28, 2016Wednesday·September 28, 2016

1. 01*

   Improved quasi parton distribution through Wilson line renormalization

   Jiunn-Wei Chen🇹🇼 · Xiangdong Ji🇨🇳 · Jian-Hui Zhang🇩🇪

   Recent developments showed that hadron light-cone parton distributions could be directly extracted from spacelike correlators, known as quasi parton distributions, in the large hadron momentum limit. Unlike the normal light-cone parton distribution, a quasi parton distribution contains ultraviolet (UV) power divergence associated with the Wilson line self energy. We show that to all orders in the coupling expansion, the power divergence can be removed by a "mass" counterterm in the auxiliary $z$-field formalism, in the same way as the renormalization of power divergence for an open Wilson line. After adding this counterterm, the quasi quark distribution is improved such that it contains at most logarithmic divergences. Based on a simple version of discretized gauge action, we present the one-loop matching kernel between the improved non-singlet quasi quark distribution with a lattice regulator and the corresponding quark distribution in dimensional regularization.

   hep-phhep-latNPB(2017)·138 citations
2. 02*

   Prospects for three-body Higgs boson decays into extra light scalars

   Alexander J. Helmboldt🇩🇪 · Manfred Lindner🇩🇪

   Within models containing a very light scalar particle coupled to the 125 GeV Higgs boson, we present the first detailed study of Higgs decays into three of these light scalars. We determine model-independent conditions which the scalar sector after electroweak symmetry breaking has to satisfy in order for the three-body channel to become relevant. Using a specific model -- the real scalar singlet-extension of the Standard Model (SM) -- we then identify scenarios, where the rates of scalar three-body Higgs decays are comparable to or even exceed those of the well-studied two-body channel. All those scenarios are shown to be compatible with current experimental and theoretical constraints. We finally argue that scalar three-body Higgs decays lead to exciting new collider signatures with six SM fermions in the final state. Calculating the corresponding event rates, we find that e.g. six-muon or six-tau final states may be in reach of dedicated searches at the LHC or ILC experiments.

   hep-phhep-exPRD(2017)·5 citations
3. 03*

   Supersymmetric $U(1{)}_{Y^{\prime }}\otimes U(1{)}_{B-L}$ extension of the standard model

   J. C. Montero🇧🇷 · V. Pleitez🇧🇷 · M. C. Rodriguez🇧🇷 · B. L. Sánchez-Vega🇧🇷

   We build a supersymmetric version with $SU(3{)}_C\otimes SU(2{)}_L\otimes U(1{)}_{Y^{\prime }}\otimes U(1{)}_{B-L}$ gauge symmetry, where $Y^{\prime }$ is a new charge and $B$ and $L$ are the usual baryonic and leptonic numbers. The model has three right-handed neutrinos with identical $B-L$ charges, and can accommodate all fermion masses at the tree level. In particular, the type-I seesaw mechanism is implemented for the generation of the active neutrino masses. We obtain the mass spectra of all sectors and for the scalar one we also give the flat directions allowed by the model.

   hep-phInt.J.Mod.Phys.A(2017)·6 citations
4. 04*

   Energy helps accuracy: electroweak precision tests at hadron colliders

   Marco Farina🇺🇸 · Giuliano Panico🇪🇸 · Duccio Pappadopulo🇺🇸 · Joshua T. Ruderman🇺🇸 · Riccardo Torre🇨🇭 · Andrea Wulzer🇮🇹

   We show that high energy measurements of Drell-Yan at the LHC can serve as electroweak precision tests. Dimension-6 operators, from the Standard Model Effective Field Theory, modify the high energy behavior of electroweak gauge boson propagators. Existing measurements of the dilepton invariant mass spectrum, from neutral current Drell-Yan at 8 TeV, have comparable sensitivity to LEP. We propose measuring the transverse mass spectrum of charged current Drell-Yan, which can surpass LEP already with 8 TeV data. The 13 TeV LHC will elevate electroweak tests to a new precision frontier.

   hep-phPLB(2017)·229 citations
5. 05*

   Search for the anomalous electromagnetic moments of the tau lepton through electron-photon scattering at the CLIC

   Y.Ozguven🇹🇷 · S. C. İnan🇹🇷 · A. A. Billur🇹🇷 · M. Köksal🇹🇷 · M. K. Bahar🇹🇷

   We have examined the anomalous electromagnetic moments of the tau lepton in the processes $e^{-}\gamma \to {\nu }_e\tau {\bar{\nu }}_{\tau }$ ($\gamma$ is the Compton backscattering photon) and $e^{-}{e}^{+}\to e^{-}{\gamma }^{\ast }{e}^{+}\to {\nu }_e\tau {\bar{\nu }}_{\tau }{e}^{+}$ (${\gamma }^{\ast }$ is the Weizsacker-Williams photon) with unpolarized and polarized electron beams at the CLIC. We have obtained 95$\%$ confidence level bounds on the anomalous magnetic and electric dipole moments for various values of the integrated luminosity and center-of-mass energy. Improved constraints of the anomalous magnetic and electric dipole moments have been obtained compared to the LEP sensitivity.

   hep-phNPB(2017)·25 citations
6. 06*

   Inclusive production of J/$\psi$ and ${\psi }^{\prime }$ mesons at the LHC

   Anna Cisek🇵🇱 · Antoni Szczurek🇵🇱

   We discuss the prompt production of $J/\psi$ mesons in proton-proton collisions at the LHC within a NRQCD $k_t$-factorization approach using Kimber-Martin-Ryskin (KMR) unintegrated gluon distributions (UGDF). We include both direct color-singlet production ($gg\to J/\psi$g) as well as a feed-down from ${\chi }_c\to J/\psi \gamma$ and ${\psi }^{\prime }\to J/\psi X$. The production of the decaying mesons (${\chi }_c$ or ${\psi }^{\prime }$)is also calculated within NRQCD $k_t$-factorization. The corresponding matrix elements for $gg\to J/\psi$, $gg\to {\psi }^{\prime }$ and $gg\to {\chi }_c$ include parameters of the nonrelativistic spatial wave functions of quarkonia at $r=0$, which are taken from potential models from the literature. We get the ratio of the corresponding of the cross sections for ${\chi }_c(2)$-to-${\chi }_c(1)$ much closer to experimental data than obtained in recent analyses. Differential distributions in rapidity of $J/\psi$ and ${\psi }^{\prime }$ are calculated and compared to experimental data of the ALICE and LHCb collaborations. We discuss possible onset of gluon saturation effects at forward/backward rapidities. One can describe the experimental data for $J/\psi$ production within model uncertainties with color-singlet component only. Therefore our theoretical results leave only a relatively small room for the color-octet contributions.

   hep-phEPJ Web Conf.(2016)·2 citations
7. 07*

   Radiatively induced Fermi scale and unification

   Tommi Alanne🇩🇰

   We propose a framework, where the hierarchy between the unification and the Fermi scale emerges radiatively. This work tackles the long-standing question about the connection between the low Fermi scale and a more fundamental scale of Nature. As a concrete example, we study a Pati-Salam-type unification of Elementary-Goldstone-Higgs scenario, where the Standard Model scalar sector is replaced by an SU(4)-symmetric one, and the observed Higgs particle is an elementary pseudo-Goldstone boson. We construct a concrete model where the unification scale is fixed to a phenomenologically viable value, while the Fermi scale is generated radiatively. This scenario provides an interesting link between the unification and Fermi scale physics, and opens up prospects for exploring a wide variety of open problems in particle physics, ranging from neutrinos to cosmic inflation.

   hep-ph0 citations
8. 08*

   Boxes, Boosts, and Energy Duality: Understanding the Galactic-Center Gamma-Ray Excess through Dynamical Dark Matter

   Kimberly K. Boddy🇺🇸 · Keith R. Dienes🇺🇸 · Doojin Kim🇺🇸 · Jason Kumar🇺🇸 · Jong-Chul Park🇰🇷 · Brooks Thomas🇺🇸

   Many models currently exist which attempt to interpret the excess of gamma rays emanating from the Galactic Center in terms of annihilating or decaying dark matter. These models typically exhibit a variety of complicated cascade mechanisms for photon production, leading to a non-trivial kinematics which obscures the physics of the underlying dark sector. In this paper, by contrast, we observe that the spectrum of the gamma-ray excess may actually exhibit an intriguing "energy-duality" invariance under $E_{\gamma }\to E_{\ast }^2/E_{\gamma }$ for some $E_{\ast }$. As we shall discuss, such an energy duality points back to a remarkably simple alternative kinematics which in turn is realized naturally within the Dynamical Dark Matter framework. Observation of this energy duality could therefore provide considerable information about the properties of the dark sector from which the Galactic-Center gamma-ray excess might arise, and highlights the importance of acquiring more complete data for the Galactic-Center excess in the energy range around 1 GeV.

   hep-phastro-ph.COastro-ph.GAastro-ph.HEPRD(2017)·34 citations
9. 09*

   CMB Delensing Beyond the B Modes

   Daniel Green🇺🇸 · Joel Meyers🇨🇦 · Alexander van Engelen🇨🇦

   Gravitational lensing by large-scale structure significantly impacts observations of the cosmic microwave background (CMB): it smooths the acoustic peaks in temperature and $E$-mode polarization power spectra, correlating previously uncorrelated modes; and it converts $E$-mode polarization into $B$-mode polarization. The act of measuring and removing the effect of lensing from CMB maps, or delensing, has been well studied in the context of $B$ modes, but little attention has been given to the delensing of the temperature and $E$ modes. In this paper, we model the expected delensed $T$ and $E$ power spectra to all orders in the lensing potential, demonstrating the sharpening of the acoustic peaks and a significant reduction in lens-induced power spectrum covariances. We then perform cosmological forecasts, demonstrating that delensing will yield improved sensitivity to parameters with upcoming surveys. We highlight the breaking of the degeneracy between the effective number of neutrino species and primordial helium fraction as a concrete application. We also show that delensing increases cosmological information as long as the measured lensing reconstruction is included in the analysis. We conclude that with future data, delensing will be crucial not only for primordial $B$-mode science but for a range of other observables as well.

   ↳ astro-ph.COhep-phhep-thJCAP(2017)·99 citations
10. 10*

    Deriving analytic solutions for compact binary inspirals without recourse to adiabatic approximations

    Chad R. Galley🇺🇸 · Ira Z. Rothstein🇺🇸

    We utilize the dynamical renormalization group formalism to calculate the real space trajectory of a compact binary inspiral for long times via a systematic resummation of secularly growing terms. This method generates closed form solutions without orbit averaging, and the accuracy can be systematically improved. The expansion parameter is $v^5\nu \Omega (t-t_0)$ where $t_0$ is the initial time, $t$ is the time elapsed, and $\Omega$ and $v$ are the angular orbital frequency and initial speed, respectively, and $\nu$ is the binary's symmetric mass ratio. We demonstrate how to apply the renormalization group method to resum solutions beyond leading order in two ways. First, we calculate the second order corrections of the leading radiation reaction force, which involves highly non-trivial checks of the formalism (i.e. its renormalizability). Second, we show how to systematically include post-Newtonian corrections to the radiation reaction force. By avoiding orbit averaging we gain predictive power and eliminate ambiguities in the initial conditions. Finally, we discuss how this methodology can be used to find analytic solutions to the spin equations of motion that are valid over long times.

    ↳ gr-qchep-phhep-thPRD(2017)·28 citations
11. 11*

    The Lambda(1405) state in a chiral unitary approach with off-shell corrections to dimensional regularized loop functions

    Fang-Yong Dong🇨🇳 · Bao-Xi Sun🇨🇳 · Jing-Long Pang🇨🇳

    The Bethe-Salpeter equation is solved in the framework of unitary coupled-channel approximation by using the pseudoscalar meson-baryon octet interaction. The loop function of the intermediate meson and baryon is deduced in a dimensional regularization scheme, where the relativistic kinetic effect and off-shell corrections are taken into account. According to the experimental data at the $K^{-}p$ threshold, the subtraction constants in the loop function are determined. The squared amplitude is suppressed strongly and only one $\Lambda (1405)$ state is generated dynamically in the strangeness $S=-1$ and isospin $I=0$ sector.

    ↳ nucl-thhep-phCPC(2017)·13 citations
12. 12*

    High-luminosity LHC prospects with the upgraded ATLAS detector

    M. Slawinska🇳🇱

    Run 1 at the LHC was very successful with the discovery of a new boson. The boson's properties are found to be compatible with those of the Standard Model Higgs boson. It is now revealing the mechanism of electroweak symmetry breaking and (possibly) the discovery of physics beyond the Standard Model that are the primary goals of the just restarted LHC. The ultimate precision will be reached at the High-Luminosity LHC phase with a proton-proton centre-of-mass energy of 14 TeV. In this contribution physics prospects are presented for ATLAS for the integrated luminosities 300/fb and 3000/fb: the ultimate precision attainable on measurements of the Higgs boson couplings to elementary fermions and bosons, its trilinear self-coupling, as well as perspectives on the searches for supersymmetric partners associated with the Higgs boson. Benchmark studies are presented to show how the sensitivity improves at the future LHC runs. For all these studies, a parametrised simulation of the upgraded ATLAS detector is used and expected pileup conditions are accounted for.

    ↳ hep-exhep-phPoS(2016)·5 citations
13. 13*

    Position-space approach to hadronic light-by-light scattering in the muon $g-2$ on the lattice

    Nils Asmussen🇩🇪 · Jeremy Green🇩🇪 · Harvey B. Meyer🇩🇪 · Andreas Nyffeler🇩🇪

    The anomalous magnetic moment of the muon currently exhibits a discrepancy of about three standard deviations between the experimental value and recent Standard Model predictions. The theoretical uncertainty is dominated by the hadronic vacuum polarization and the hadronic light-by-light (HLbL) scattering contributions, where the latter has so far only been fully evaluated using different models. To pave the way for a lattice calculation of HLbL, we present an expression for the HLbL contribution to $g-2$ that involves a multidimensional integral over a position-space QED kernel function in the continuum and a lattice QCD four-point correlator. We describe our semi-analytic calculation of the kernel and test the approach by evaluating the ${\pi }^0$-pole contribution in the continuum.

    ↳ hep-lathep-phPoS(2016)·59 citations
14. 14*

    Extraction of the ${\pi }^{+}{\pi }^{-}$ Subsystem in Diffractively Produced ${\pi }^{-}{\pi }^{+}{\pi }^{-}$ at COMPASS

    Fabian Krinner (for the COMPASS collaboration)🇩🇪

    The COMPASS experiment at CERN has collected a large data sample of 50 million diffractively produced ${\pi }^{-}{\pi }^{+}{\pi }^{-}$ events using a $190$GeV$/c$ negatively charged hadron beam. The partial-wave analysis (PWA) of these high-precision data reveals previously unseen details. The PWA, which is currently limited by systematic uncertainties, is based on an isobar model, where multi-particle decays are described as subsequent two-body decays and where a prior-knowledge parametrization for the intermediate two-pion resonances has to be assumed -- usually a Breit-Wigner amplitude -- thus increasing systematic uncertainties, due to the concrete choice of the parametrization. We present a novel method, which allows to extract isobar amplitudes directly from the data in a less biased way. The focus lies on the scalar ${\pi }^{+}{\pi }^{-}$ subsystem, where a previous analysis found a signal for a new axial-vector state $a_1(1420)$ decaying into $f_0(980)\pi$.

    ↳ hep-exhep-phJPS Conf.Proc.(2017)·1 citation
15. 15*

    The fate of bound systems through Sudden Future Singularities

    Leandros Perivolaropoulos🇬🇷

    Sudden singularities occur in FRW spacetimes when the scale factor remains finite and different from zero while some of its derivatives diverge. After proper rescaling, the scale factor close to such a singularity at $t=0$ takes the form $a(t)=1+c|t{|}^{\eta }$ (where $c$ and $\eta$ are parameters and $\eta \ge 0$). We investigate analytically and numerically the geodesics of free and gravitationally bound particles through such sudden singularities. We find that even though free particle geodesics go through sudden singularities for all $\eta \ge 0$, bound systems get dissociated for a wide range of the parameter $c$. For $\eta <1$ bound particles receive a diverging impulse at the singularity and get dissociated for all positive values of the parameter $c$. For $\eta >1$ (Sudden Future Singularities (SFS)) bound systems get a finite impulse that depends on the value of $c$ and get dissociated for values of $c$ larger than a critical value $c_{cr}(\eta ,{\omega }_0)>0$ that increases with the value of $\eta$ and the rescaled angular velocity ${\omega }_0$ of the bound system. We obtain an approximate equation for the analytical estimate of $c_{cr}(\eta ,{\omega }_0)$. We also obtain its accurate form by numerical derivation of the bound system orbits through the singularities. Bound system orbits through Big Brake singularities ($c<0$, $1<\eta <2$) are also derived numerically and are found to get disrupted at the singularity. However, they remain bound for all values of the parameter $c$ considered.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2016)·18 citations
16. 16*

    Novel phases in strongly coupled four-fermion theories

    Simon Catterall🇺🇸 · David Schaich🇺🇸

    We study a lattice model comprising four massless reduced staggered fermions in four dimensions coupled through an $SU(4)$-invariant four-fermion interaction. We present both theoretical arguments and numerical evidence that no bilinear fermion condensates are present for any value of the four-fermi coupling, in contrast to earlier studies of Higgs--Yukawa models with different exact lattice symmetries. At strong coupling we observe the formation of a four-fermion condensate and a mass gap in spite of the absence of bilinear condensates. Unlike those previously studied systems we do not find a ferromagnetic phase separating this strong-coupling phase from the massless weak-coupling phase. Instead we observe long-range correlations in a narrow region of the coupling, still with vanishing bilinear condensates. While our numerical results come from relatively small lattice volumes that call for caution in drawing conclusions, if this novel phase structure is verified by future investigations employing larger volumes it may offer the possibility for new continuum limits for strongly interacting fermions in four dimensions.

    ↳ hep-latcond-mat.str-elhep-phPRD(2017)·45 citations
17. 17*

    CP-violating phase on magnetized toroidal orbifolds

    Tatsuo Kobayashi🇯🇵 · Kenji Nishiwaki🇰🇷 · Yoshiyuki Tatsuta🇯🇵

    We study the CP-violating phase of the quark sector in the $U(8)$ flavor model on $T^2/Z_N(N=2,3,4,6)$ with non-vanishing magnetic fluxes, where properties of possible origins of the CP violation are investigated minutely. In this system, a non-vanishing value is mandatory in the real part of the complex modulus parameter $\tau$ of the two-dimensional torus. On $T^2$ without orbifolding, underlying discrete flavor symmetries severely restrict the form of Yukawa couplings and it is very difficult to reproduce the observed pattern in the quark sector including the CP-violating phase ${\delta }_{\mathrm{CP}}$. In cases of multiple Higgs doublets emerging on $T^2/Z_2$, the mass matrices of the zero-mode fermions can be written in the Gaussian textures by choosing appropriate configurations of vacuum expectation values of the Higgs fields. When such Gaussian textures of mass matrices are realized, we show that all of the quark profiles, which are mass hierarchies among the quarks, quark mixing angles, and ${\delta }_{\mathrm{CP}}$ can be simultaneously realized.

    ↳ hep-thhep-phJHEP(2017)·47 citations
18. 18*

    Comprehending particle production at RHIC and LHC energies using global measurements

    Sadhana Dash🇮🇳 · Basanta K. Nandi🇮🇳 · Ranjit Nayak🇮🇳 · Ashutosh Kumar Pandey🇮🇳 · Priyanka Sett🇮🇳

    The centrality dependence of the charged-particle multiplicity densities ($d{N}_{ch}/d\eta$) and transverse energy densities ($d{E}_T/d\eta$) are investigated using the two-component Glauber approach for broad range of energies in heavy ion collisions at RHIC and LHC. A comprehensive study shows that the data is well described within the framework of two component model which includes the contribution of "soft processes" and "hard processes" for different centrality classes and energies. The data at two different energies are compared by means of the ratio of $d{N}_{ch}/d\eta$ (and $d{E}_T/d\eta$) to see the interplay of energy and $x$-scaling.

    ↳ nucl-thhep-phMod.Phys.Lett.A(2017)·1 citation
19. 19*

    Three-body system of $\pi \pi {\Sigma }_c$

    Bingwei Long🇨🇳

    The existence of near-threshold charmed baryon ${\Lambda }_c(2595{)}^{+}$ implies that the pion and the lightest, isospin-$1$ charmed baryon ${\Sigma }_c$ interact very strongly at extremely low energies. Using the two-flavor version of heavy hadron chiral perturbation theory, I explore the direct consequences of this strong force by investigating whether the ${\Sigma }_c$ can trap two very soft pions to form any visible hadronic states. The answer is positive. It is found without tuning any free parameters or ultraviolet cutoff that the state in question, with quantum numbers $I(J^P)=1({\frac{1}{2}}^{+})$, presents itself as a resonance pole only a few MeVs away from the $\pi \pi {\Sigma }_c$ threshold. Subleading corrections are estimated with power-counting arguments, and the smallness of pion momenta is found to facilitate the reliability of the analysis. Because of its proximity in mass, this excited ${\Sigma }_c$ resonance is speculated to be related to the broad resonance labeled as ${\Lambda }_c^{+}(2765)$.

    ↳ nucl-thhep-exhep-ph3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.